The present invention relates to a battery unit with a plurality of cell assemblies.
One type of known battery unit is provided with a plurality of cell assemblies connected in parallel and is configured to be able to supply power to the load of a power supply target from at least one of the plurality of cell assemblies. Each of the plurality of cell assemblies has a plurality of battery cells (hereinafter, simply referred to as “cells”) that are connected in series, parallel or series-parallel. For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2011-218510, the battery unit of this type may be configured such that the plurality of cell assemblies are accommodated in a housing or the plurality of cell assemblies are individually attachable and detachable from the battery unit.
In the battery unit like this, in case that the plurality of cell assemblies are simply connected in parallel, there is a possibility that a sneak (backflow) current from one cell assembly to another cell assembly is generated due to differences in the electrical state, etc. between the cell assemblies. Such backflow is less preferred in light of quality maintenance of the battery. The reason is because, if abnormality occurs to one of the cell assemblies, it is possible that an excessive sneak (charge) current from the other parallel-connected cell assemblies to the cell assembly in the abnormal state is generated, thereby worsening the situation.
In contrast, Japanese Unexamined Patent Application Publication No. 2011-218510 discloses an adapter configured to connect a diode to a positive electrode of each battery, and to output a current to the load from each battery via the diode. With this adapter, a sneak current between the parallel-connected batteries is blocked by the diode.